I don't have a long run, I don't think.So as long as you do something after the penetration to slow down the air again, then give it a long straight run after that so the turbulence dissipates, then you should be fine.
The plan at this point is to have the silencer box (roughly 9" path on the inside) that connects to the square wooden duct (pictured in attached) that will be either 6" or 9" square. That runs through the wall for about a foot and then opens directly into the room.
Does any of that count as a long run?
Is it ok if I have the 9" silencer path connect directly to the 9" wooden duct? Would it be better to have a 6" hole at the end of the silencer instead of a 9" hole... and have that 6" hole connect into the 9" duct immediately and then run for a foot?
I'm genuinely stuck here and really, really want to build this right.
Thank you
A long run basically means a distance of at least three times (preferably five times) the "diameter" of the duct, after the last change in direction. If the duct is rectangular section instead of round, then "diameter" means the largest dimension (width or height). So if your duct is 6" square then you should have at least 18" (preferably 30")from the point where the curve ends to the point where the register is located, in order to allow for the turbulence to smooth out.